Hot Metal Hot metal (HM) is the output of a blast furnace (BF). It is liquid iron which is produced by the reduction of descending ore burden (iron ore lump, sinter, and pellet) by the ascending reducing gases. HM gets collected in the hearth of the BF. From the hearth, the HM is tapped from the taphole of the BF after an interval of time. Normally in large BFs, HM tapping rates of 7 ton/min and liquid tapping velocities of 5 m/sec, in tap holes of 70 mm diameter and 3.5 m long, are typically encountered. The tapping rate of HM is strongly influenced by the taphole condition and taphole length. Generally the temperature of tapped HM varies in the range of 1420 deg C to 1480 deg C. The tapped HM is handled in the two stages namely (i) handling of the HM in the cast house i.e. from taphole to the hot metal ladles (open top or torpedo), and (ii) transport of HM ladles to the point of HM consumption. Presently most of the HM is consumed within integrated steel plants for steel making. The HM is transferred to the steel melting shop for making of steel. The HM which is not sent for steel making is cast into pig iron in pig casting machine for use in steel making later as cold charge or is sold to foundries or to mini steel plants having induction furnaces as merchant pig iron. HM can also be granulated by a process which is known as ‘Granshot’ process. Presently the Granshot plants for the production of GPI are working at six places namely (i) Uddeholm, Sweden, (ii) SSAB Lulea, Sweden, (iii) Voest Alpine, Donawitz, (iv) Saldanha steel, South Africa, (v) SSAB Oxelosund, Sweden, and (vi)...

Importance of Hearth, Dead man and Tapping in Blast Furnace Operation A trend of deterioration in ore quality is seen these days with the increasing demand for iron ore. The deterioration in ore quality is accompanied with higher quantities of slag which in turn affects burden descent and liquid flow through the hearth. These conditions provide a catalyst for lining wear mechanism with bosh, stack and hearth linings coming under additional stress. Tapping in the blast furnace is adversely affected and trough and runners in the cast house get under strain due to higher slag volume. All these put increased pressure on blast furnace operations. The poor quality of iron ore affects the operation of the blast furnace in the following way. Slag volume – Poor quality of iron ores bring into the furnace higher quantities of impurities resulting into increase in the slag volumes. Heat load – The furnace thermal condition undergoes changes since a large quantity of heat is required to melt the additional slag as well as to keep it in proper fluid state for its drainage. This introduces higher heat loads inside the blast furnace. Coke rate and productivity – Increasing slag volumes needs a higher fuel input into the furnace, and where pulverized coal injection rates are already running at optimum, this results into a higher coke rate. Higher coke means introduction of higher amount of ash in the furnace resulting into further increase in the slag volume. This has got a deteriorating effect on the productivity of the furnace. Process stability – The deterioration in the ore quality affects the process stability adversely and has an unfavourable effect on the smooth running of the blast furnace. Due to the above factors, the production process in the blast furnace...

Blast Furnace Tap Hole and Tapping of the Furnace The operation of a blast furnace is a continuous process. The blast furnace continues to produce liquid iron (hot metal) and slag as long as it is in operation. The hot metal and slag accumulate in the hearth of the furnace, but since there is a limit to the amount that can be accumulated before it interferes with the furnace operation, hot metal and slag must be removed from the furnace at regular intervals. The tap hole also known as iron notch, is used for tapping the hot metal from the furnace. It is located slightly above the floor of the hearth. Regardless of the specific tap hole configuration or operating philosophy, due to the addition of dynamic (often periodic) and more intense process conditions (exposure to higher temperatures leading to accelerated corrosion, greater turbulence, and elevated rates of mass and heat transfer), and higher concurrent thermo-mechanical forces (from thermal or flow shear stresses), the performance and longevity of the blast furnace is intimately linked to the performance of the tap hole. Hence tap hole is very critical to the blast furnace. It is the heart and the lifeline of the blast furnace since without a tap hole a blast furnace cannot exist. The criticality and relevance of tap hole continues even in the modern automated blast furnaces. Tap hole is an essential part of a blast furnace. Large furnaces usually have 2 to 4 tap holes and the drainage of hot metal and slag is practically continuous by periodically drilling and plugging the tap holes with one of the tap holes is always open and two alternate tapings usually overlap for some period of time. Medium or small sized blast furnaces have normally one...

Design Features of an AC Electric Arc Furnace Electric arc furnace (EAF) used for steel making apply high current and low voltage electric energy to the charge materials , and thereby melt and refine them. EAF is a batch furnace which consists of a refractory lined vessel covered with a retractable roof through which electrodes enter the furnace. General features of a typical AC electric arc furnace is shown in Fig 1. Fig 1 General features of an AC electric arc furnace EAF has a large bowl shaped body with a dish shaped hearth. The shell has a refractory lining inside. The reaction chamber of the furnace is covered from above by a removable roof made of refractory bricks held by a roof ring. It is fed with a three phase alternating current (AC) and has three graphite electrodes which are connected by flexible cables and water cooled copper tubes. The design of electric arc furnaces has changed considerably in recent years. Emphasis has been placed on making furnaces larger, increasing power input rates to the furnace and increasing the speed of furnace movements in order to minimize power off time in furnace operations. Modern steel melting shops with EAFs usually employ a mezzanine furnace installation. In this type of installation, the furnace sits on an upper level above the shop floor. The furnace is supported on a platform which can take on several different configurations. In the half platform configuration, the electrode column support and roof lifting gantry is hinged to the tiltable platform during operation and tapping. When charging the furnace, the complete assembly is lifted and swiveled. This design allows for the shortest electrode arm configuration. In the full platform design, the electrode column support and roof lifting assembly is completely...